The most common way to tune a membranous percussive musical instrument usually involves manually adjusting the tension of the membrane in order to achieve the desired frequency. In the case of a drum, the resonant frequency of the drum depends on the tension of the membrane or drum head, which is stretched over and joined with a shell by a hoop/ring that is fastened to lugs on the shell by uniformly spaced bolts, which are commonly referred to as tension rods. The first step in tuning a drum is to “clear” the drum head. This process involves equalizing the tension of the drum head near each tension rod to achieve a uniform vibration throughout the entire drum head. Once this is complete, the drum has uniform resonant properties, which result in a clear tone when excited, and can then be tuned to the desired frequency, i.e., note. This process is fairly time consuming and relies on the expertise and judgment of the user to achieve an accurate result.
There are approximately 18 million people in the United States who currently play drums. Unlike other instruments, for example a guitar, drums are very difficult to tune to a desired note. In order to tune a guitar, the tension in each string is adjusted separately in order to achieve the correct frequency. A drum cannot be tuned the same way. A drum head has six or eight tension rods, which sit on the outside of the drum head and are joined with corresponding lugs that are on the outside of the drum shell. When one of these tension rods is tightened or loosened, it will change the tension in the drum head. When the tension at one of these tension rods is adjusted, it will affect the entire drum head, not just the area of the drum head adjacent the particular tension rod. This is a time consuming and imprecise method.
Because of the complexity of tuning a drum, there is very little literature beyond the instructions for manually tuning a drum. An example of step-by-step manual instructions for tuning a drum include the following:
1. Choose a tension rod to act as your model tension rod, this will be how you know you have tuned all the tension rods on each tuning pass;
2. Tap the drum head with the stick gently, approximately 2 inches from the tension rod in the direction of the center of the drum, this is your test tone;
3. Continuing with the tension rod on the opposite side of the drum from the model tension rod, tap on the head gently. Using a standard drum key, a hand tool for turning tension rods as known in the art, turn the tension rod until the tone is the same as the original tone;
4. Moving in a star formation tap on the drum head by the next tension rod;
5. Repeat step 3;
6. Repeat step 4 followed by step 3 until you have returned to the model tension rod; and
7. Now test the tone of the center of the drum. If you are satisfied with the tone, then you are done. If not satisfied, then again starting with the model tension rod, turn each tension rod one-quarter turn moving clockwise around the drum until you reach the model tension rod again.
Existing products that assist a user to tune a drum reliably using resonant frequency technology are not autonomous and force the user to manually tune the drum. One such product acquires the frequency at each tension rod by using a speaker to drive the drum and a microphone to measure the resonant response. It stores all of the frequencies as the user manually rotates the device from tension rod to tension rod and chooses a mean value that one must tune to in order to clear the drum head. The user can then choose a frequency that he or she wants and turn the lug until the device says it is there. However, this requires that the user iteratively repeat this process of rotating and collecting data until he or she has achieved the desired result.
Another known product is an adjustable release torque wrench. The wrench releases at a mechanically determined torque limit. The user, therefore, must turn each lug until the wrench releases, resulting in the torque in each lug being equal. The downside of this design, however, lies in the assumption that torque will directly correlate to tension on the membrane. This would only prove successful if the friction in each lug was equal. In actuality, and as proved in testing, the friction in each lug will vary significantly depending on the level of lubrication and tolerance fit of the actual thread fit. The user is therefore limited to an inaccurate method that relies on unrealistic assumptions.